Process of producing unsaturated products



Patented May 10,1949

PROCESS OF PRODUCING 'UNSATURATED PRODUCTS Ivor M. Colbeth, Maplewood,N. J., assignor to The Baker Castor Oil Company, Jersey City, N. J acorporation of New Jersey No Drawing. Application March 6, 1946, SerialNo. 652,491

Claims. (Cl. 260-4055) This invention relates to treatment of higherfatty acid esters of monohydric and dihydric alcohols in such a way thatproducts result therefrom that have a higher degree of unsaturation thanthe esters from which they were made. Such products are particularlyuseful in the production of resins, varnishes, and other dryingproducts, as they aid in the formation and plasticization of films whichsolidify by the process of oxidation and/or polymerization.

This is a continuation-in-part of my now abandoned application SerialNo. 434,093, filed March 10, 1942. Reference is also made to my PatentsNos. 2,278,425, 2,317,361 and 2,317,362.

The products formed hereby are usually viscous liquids having dryingproperties. They are pale in color and will dissolve in the usualorganic solvents that are used in the paint industry, such asturpentine, solvent naphtha, ethyl acetate, gasoline, etc. They arevaluable, for example, for replacingother materials such as linseed oilacids, China-wood oil acids, and, to a certain extent, linseed oil andChina-wood oil.

The substances made in accordance with the present invention do not havethe same strong drying properties as similar substances prepared fromglycerides, but they are of distinct value in that they are valuableplasticizers for resins that are used in varnishes and lacquers, and forthe more rapid drying oils.

One of the advantages of using the process of the present invention informing the unsaturated ester-type plasticizers is that the resultingproducts have greater resistance to darkening or discoloration andgreater resistance to alkali than products formed by previously knownprocesses.

A large part of this superiority is due to the fact that conjugateddouble bonds are formed in the ester molecules during the treatment ofthe initial esters according to the process of this invention.

The products of this invention may be used in the synthesis of alkyds inmuch the same manner that glycerides are so employed. Theywill combinewith oxygen as do the drying oils. They may be caused to polymerize in areasonably short length of time in the presence of catalysts, such asboron trifiuoride, zinc chloride, and naphthalene sulfonic acid.

In carrying out this invention, fatty acids are esterified in the knownway with a monohydric or dihvdric alcohol, such as butyl alcohol. benzvlalcohol, or ethylene glycol. The fatty acids to be used may, forexample, be obtained by the bonds.

hydrous hydrogen chloride;

2 table oils, or by the oxidation of long chain paraffln hydrocarbons.Those esters, formed from such fatty acids, which are not esters ofsaturated polyhydroxy or unsaturated monoor poly-hydroxy' acids areconverted into such esters, as by oxidation, before being treatedaccording to the process of this invention. In effect, then, the esterswhich are treated by this invention are the esters of such fatty acidsas ricinoleic acid, dihydroxy oleic acid, and aleuritic acid which is atrihydroxy palmitic acid.

Various methods may be used for oxidizing the esters of the acids whichdo not contain the desired number of hydroxyl groups. This oxidation,and the resulting introduction of hydroxyl groups into the fatty acidchains, may be accomplished by the use of air, oxy en, or ozone. 0r suchoxidizing agents as chlorine, iodine, etc., may be used in' theoxidizing step and the hydroxyl groups may then be formed by treatmentwith alkalis, such as aqueous sodium hydroxide. Oxidizing agents such aspotassium permanganate in dilute alkali solution may be used whendesired. More than one oxidizing agent may be used for the introductionof hydroxyl groups into the ester molecules. ,These agents may be usedin sequence. For example, the ester may be treated with a dilutealkaline solution of potassium permanganate whereupon hydroxyl groupsbecome attached to the fatty acid chains at the positions previouslyoccupied by the double Additional hydroxyl groups can then be introducedby chlorination of this hydroxy compound, after which the chlorinegroups are transformed into hydroxyl groups through the medium of anaqueous alkali. As an alternative to the treatment with potassiumpermanganate, unsaturated esters may also be treated with anfurtherchlorine atoms are then introduced by chlorination, and thehydroxylation step is carried out as before.

In carrying out this invention esters of monohydric or dihydric alcoholsand hydroxy acids of the sorts mentioned above are treated with a boroncompound to form soluble ester-type plasticizers with some dryingproperties. The reaction with the boron compound serves to remove thehydroxyl groups from the fatty acid chains in the ester molecules,thereby, yielding esters of fatty acids having at least two double bondsper fatty acid chain. The reaction of the hydroxy ester with the boroncompound is carried out at a suitable temperature in the range fromabout to about 260 C. Ester linkages are formed between the boroncompound and the hydroxyl groups of the hydroxy esters in this reaction.Following the completion of this reaction. the reaction mixture isheated to a somewhat higher temperature in the range from about 190 toabout 300 C. in order to bring about the decomposition of the initiallyformed boron-containing esters and produce unsaturated esters so that nohydroxyl groups will be attached to the fatty acid chains.

A mixture of the hydroxy ester and .the boron compound may be heatedslowly to the initial reaction temperature, or the hydroxy ester may beheated to the reaction temperature and the boron compound added in smallincrements. The amount of boron compound used in this process is usuallyfrom about 0.1 to about 4.0%, based on the amount of the hydroxy ester.Physical test methods, such as the determination of the refractiveindex, may be utilized in checking the completeness of thedehydroxylation reaction in any given instance; but, in general, thereaction is continued until the acetyl value of the product is at leastless than 10. The reaction may even be carried to the point Where theacetyl value is practically zero. this reaction with a boron compoundand the subsequent decomposition reaction in an atmosphere free fromoxygen. Such an atmosphere may be attained by evacuating the reactionsystem, or by maintaining an inert gas in this system.

It is preferred to carry out moreover, that the extent of conversion ofthe hydroxy esters to unsaturated compounds is very much more completethan is the case with other catalysts. This is indicated by the loweracetyl values which may be obtained readily by the use of boronpyrosulfate as the catalyst. Since, when boron pyrosulfate is used, thereaction may be conducted at a relatively low temperature, very littlehydrolysis of the ester takes place, and the acid value of the finishedester is but slightly higher than that of the original hydroxy ester.

By preparing boron derivatives of hydroxy esters by adding any compoundof boron which will react with the hydroxy] groups, such as metallicborates, boric acid, boric anhydride, halides of boron, sulfates,acetates, and other organic compounds of boron, and then adding to theresulting product from 0.1 to 0.25% of sulfuric acid, products areformed similar to those described above. The sulfuric acid causes theboron derivatives of the hydroxy esters to be decomposed with theelimination of water, and

iii).

The products of this invention are quite pale in color. The acid valueof the products can be maintained below about 5 by proper regulation ofthe temperature and the vacuum. The acid value generally ranges fromless than 1 to about 2. The viscosity of the final products can becontrolled by the length of time of treatment with the boron compoundand the temperature at which the reactions are carried out.

Various boron compounds, such as boric acid, boric anhydride, borax, andboron pyrosulfate, may be used in the process of this invention. It hasbeen found that, since boric acid is dificultly soluble in water andalso since it is desirable to introduce it into the hydroxy ester insuch a way that it does not become occluded in masses of solidifiedester, thus preventing its complete reaction with the ester, borax canfirst be dissolved in water and then decomposed with mineral acids andthe entire solution gradually fed into the reacting vessel containingthe hot ester. The rapid evaporation of the solution producesmicroscopic crystals of boric acid which are more readily dissolved bythe ester and also facilitates better control of the reaction.

In general, the greater the amount of boron reagent used, the darker isthe color of the resulting products, the lower the temperature of thereaction, the lighter is the color of the resulting products; and theshorter the time of the reaction, the lighter is the color of theresulting products. The use of boron pyrosulfate as the boron reagentbrings about improved reaction conditions in all three of theseconditions.

The boron pyrosulfate may be ground and added to the ester as a powder,but better results are obtained if the ester is heated to reactiontemperature and a mixture of borax or boric acid or boric anhydride andsulfuric acid in the proper proportions to form the boron pyrosulfate isintroduced into the ester. The time of reaction is decreasedapproximately 6 when the, ester is treated with only about 0.1 to 0.25%of the boric and sulfuric acid compound or boron pyrosulfate as comparedto the time required when unsaturated esters of lower viscosity, higherrefractive index, lighter color, and lower acid value than is possiblewithout the use of boron pyrosulfate, are thus produced. It hasbeenfound that when the amount of borax is increased to twice thetheoretical amount required for the preparation of the sodium borylpyrosulfate, the resulting-products appear to be as advantageous as thesodium boryl pyrosulfate and they have the additional advantage ofkeeping the acid value of the unsaturated esters at a minimum.

The following examples are given to illustrate the invention, but it isto be understood that the invention is not limited to these examples.

Example 1 Ricinoleic acid is esterified with butyl alcohol using 0.5% ofsulfuric acid as a catalyst. When the esterification is complete, thesulfuric acid is removed by treating the reaction mixture withprecipitated chalk; the excess butyl alcohol is removed by distillation;and the ester is freed from the chalk by filtration. The ester soprepared is then mixed with about 1.0%, based on the ester, of borylpyrosulfate, BOHSzOv, and this mixture is heated to and maintained atapproximately 225 C. After a short time, the temperature is increased toapproximately 250 C., and v the reaction mixture is kept at thistemperature until the reaction is substantially complete. This isindicated when the acetyl value of the butyl ester falls below about 10.During the heating period, an atmosphere of nitrogen is maintained overthe reaction mixture, so that substantially no oxidation of theunsaturated butyl ester will occur. The product resulting from thistreatment is highly unsaturated, the iodine number having increased toabout to 150.

Example 2 l-rali, whereupon the chlorine is removed and is very largelyreplaced by hydroxyl groups. The

5. The reaction mixture is maintained in contact with a nitrogenatmosphere while the reaction is in progress.

The highly unsaturated ester formed in this treatment may be used in thepreparation of alkyd resins. It is also eminently satisfactory for useas a plasticiz-eriora variety of'plastic materials, including cellulose.ethers and esters, natural and synthetic resinous materials, andsynthetic rubbers.

Example 3 9,10-dihydroxystearic acid, obtained by oxidizing elaidic acidwith hydrogen peroxide in acetic acid, is esterified with benzyl alcoholusing sulfuric acid as a catalyst. The ester is heated to about 230 C.,in a nitrogen atmosphere, and a solution obtained by dissolving borax inwater and then decomposing the borax with a mineral acid, is graduallyadded to the hot ester. Approximately 2 to 3% of boric acid, based onthe ester, is added in this Way. After a short time,

the temperature is increased to about 260 C., and kept at thattemperature until the acetyl value of the ester indicates that thedehydration reaction is complete. A highly unsaturated ester which is avaluable plasticizer is obtained as a result of this treatment. i

Example 4 Example 5 Hydroxy acids obtained by the oxidation of longchain hydrocarbons, such as those obtainable from petroleum or bysynthetic methods, e. g., the Fischer-Tropsch synthesis, are esterifiedwith 2,3-butylene glycol. The resulting ester is mixed with about-10.5%of boryl pyrosulfate, and the mixture is heated to about 215 C. under areduced pressure. The temperature is subsequently raised to about 235C., and held ture of about 200 C. Subsequently, the temperature israised to approximately 225 C., and maintained at this point untildehydration of the butyl ester is substantially complete. The reactionmixture is blanketed with nitrogen during the heating period. The highlyunsaturated esterwhich is formed is a valuable constituent of resins andvarnishes.

Example 7 The heptyl ester of di-hydroxy oleic acid is subjected to atreatment corresponding to that of Example 6. The product obtained is auseful, unsaturated ester-type plasticizer.

I claim:

1. The process which comprises reacting an ester of a monobasic, hydroxyfatty acid and of a straight chain alcohol, said alcohol having not atthis point until dehydration of the ester is substantially complete. Theresulting unsaturated ester has valuable softening and plasticizingproperties for plastic materials.

Example 6 The butyl ester of aleuritic acid is heated with about 0.35%of boryl pyrosulfate to a temperamore than two hydroxyl groups permolecule and having a boiling point not higher than about 205C., with aboron compound chosen from the group consisting of boric acid, boricanhydride, metallic borate's, and the sulfate, pyrosulfate, halides, andacetate of boron to increase the unsaturation of the ester and toproduce a pale viscous product, said reaction between said ester andsaid boron compound being efiected by heating the reaction mixture to atleast 180 C. and to not more than 260 C. until the boron esters areformed, and continuing the heating at an increased temperature in therange from C.

to 300 C. until the dehydration reaction is substantially complete.

a is ricinoleic acid.

3. The process of claim 1, in which said acid is dihydroxy oleic acid.

4. The process of claim 1, in which said alcohol is butyl alcohol.

5. The process of claim 1, in which said alcohol is ethylene glycol.

6. The process of claim 1, in which said boron compound is boric acid.

7. The process of claim 1, in which said boron compound is boronpyrosulfate.

8. The process of claim 1, in which said acid is a dihydroxy stearicacid.

9. The process of claim 1, in which the amount of said boron compoundused is 0.14.0%, based on the amount of ester.

10. The process of claim 1, in which said reaction is carried out at asub-atmospheric pressure.

11. The process of claim 1, in which said reaction is carried out in thepresence of an inert gas.

12. The process of claim 1, in which said reac tion is continued untilthe acetyl value of the product is less than 10.

13. The process of claim 1, in which the reaction between said ester andsaid boron compound is effected by initially heating the reactionmixture to at least 200 C. and by subsequently raising the temperatureto not more than 275 C. until the dehydration reaction is substantiallycomplete.

14. The process which comprises reacting an ester of a monobasic,hydroxy fatty acid and of a straight chain alcohol, said alcohol havingnot more than two hydroxyl groups per molecule and having a boilingpoint not higher than about 205 C., with boron pyrosulfate to increasethe unsaturation of the ester and produce a pale viscous product, saidboron pyrosulfate being formed in situ in the ester by the treatment ofa. compound of boron with sulfuric acid, said compound of fatty groups,and said reaction between said ester and said .boron pyrosulfate beingeffected by heating REFERENCES cum) the reaction mixture to at least 210C. and to not The following references are of record in the more than230 Cluntil a boron ester is formed, file of this patent:

and continuing heating the reaction mixture to 5 at least 235 0. and tonot more than 260 0. UNITED STATES PATENTS until the dehydrationreaction is substantially Number Name v Date complete. 7 2,125, 44Colbeth Aug. 2, 1938 15. The process of claim 14 in which said com-2,278,426 Colbeth Apr. 7, 1942 pound of boron is boric acid. 102,278,427 Colbeth Apr. 7, 1942 2,317,361 Colbeth Apr. 27, 1943 IVOR M.COLBETH. 2,317,362 Colbeth Apr. 27, 1943

